As used herein, the term “floating wind turbine” means a wind turbine structure of the kind that is designed to float in a body of water when in use. Conventional floating wind turbines comprise a buoyant body having at its upper end a nacelle, which contains an electrical generator and other components, and a rotor. The body is generally long and approximately cylindrical in shape.
Offshore floating wind turbines are very large structures, the body being typically 100-200 meters in length and the rotor blades in the range of 40-70 meters long. They are assembled on shore or in protected waters and it is a significant challenge to move them to their desired location out at sea.
One approach is to tow them out to their installation sites through the water, whilst floating in the same, generally vertical, position in which they are used. This prevents the generator from being submerged under water or splashed, which could damage its components.
With this method, the choice of an installation site for the wind turbine and the possible routes thereto are therefore limited by the depth of the water through which the wind turbine must pass. If the water in a region is too shallow, the floating wind turbine cannot be towed through that region making some installation sites unreachable, or only reachable via an indirect, longer route.
As an alternative, methods of transporting wind turbines in an essentially horizontal position are known. However, these methods require a large vessel on which the wind turbine is supported in order to keep the delicate rotor and generator components away from the water. For example, GB 2423108 discloses mounting structures, such as offshore wind turbines, using socket foundations. The mounting structure is transported to the socket in an essentially horizontal (reclined) position, on board another vessel. In another example, GB 2344843 discloses a gravity securing system for offshore generating equipment. The generating equipment is towed to the installation site in an essentially horizontal (reclined) position, again on board another vessel. It will be appreciated that the use of such vessels increases the cost of transporting the wind turbine and their size may also restrict the choice of route or installation location.